Yesterday, I was talking with a manufactured home company who had been approached by a firm (originally from Germany) who was selling a system that ran PEX tubing through the walls of a home, then into a deep pit under the home that circulated air through the PEX that was supposed to keep the home cool in the summer and warm in the winter in the Arizona desert.  They didn't remember the name of the company or their phone number. 

Has anyone heard of such a system?  Who makes it?  Does it work??

Nope.

Let us know if you find out more, but remeber that with radiant tube, density is the problem. Even with water cirulated through the tubes (that is augmented), you could fall short on heating or cooling depending on location.

Air through PEX?

No way my ductulator goes anywhere NEAR low enough...how many CFM goes through a 3/4" PEX pipe...at what friction rate?

I have had some success with burying 400' of 8" pipe 6' underground and bringing the air into the home; pex in the walls with just air... doesn't seem feasible, I would like more information.